Rapid detection of mycobacteria in clinical specimens by using the automated BACTEC 9000 MB system and comparison with radiometric and solid-culture systems.

Recovery rates of acid-fast bacilli (AFB) and the mean time to their detection from clinical specimens were determined by using the fluorescent BACTEC 9000 MB system. Data were compared to those assessed by the radiometric BACTEC 460 system and by cultivation on solid media. A total of 3,095 specimens were processed with N-acetyl-L-cysteine-NaOH by two laboratories. The contamination rates for the BACTEC 9000 MB system were 6.8% (center 1) and 9.8% (center 2). A total of 451 mycobacterial isolates were detected (Mycobacterium tuberculosis complex, n = 296; nontuberculous mycobacteria [NTM], n = 155). These isolates originated from 94 (20.8%) smear-positive and 357 (79.2%) smear-negative specimens. The BACTEC 9000 MB system was significantly better than solid media (P < 0.05) in detecting AFB, but it was less efficient than the radiometric system (P < 0.01). The BACTEC 9000 MB system plus solid media (combination A) recovered 393 (87.1%) of the isolates, while the BACTEC 460 system plus solid media (combination B) detected 430 (95.3%) of all AFB isolates. Between combination A and B there was no statistically significant difference for the detection of isolates from smear-positive specimens (P > 0.05), in contrast to the recovery of AFB from smear-negative specimens for M. tuberculosis complex, P < 0.05; for NTM, P < 0.01). The mean time to detection of M. tuberculosis complex was 12.2 days for smear-positive specimens and 18.1 days for smear-negative specimens with the BACTEC 9000 MB system; 9.3 and 15.6 days, respectively, with the BACTEC 460 system; and 21.2 and 28.4 days, respectively, with solid media. For NTM, the average detection times were 15.1, 17.3, and 31.3 days by the three methods, respectively. In conclusion, the BACTEC 9000 MB system is a rapid, less labor-intensive detection system which allows for higher levels of recovery of AFB than solid media. There is no risk of cross contamination, which is known to be the case for the BACTEC 460 system, and data management is greatly facilitated. As a whole, however, the BACTEC 9000 MB system should only be used in conjunction with solid media.

Comparison of the Mycobacteria Growth Indicator Tube (MGIT) with radiometric and solid culture for recovery of acid-fast bacilli.

In a multicenter study involving three reference centers for mycobacteria, the rate of recovery of acid-fast bacilli (AFB) and the mean time to their detection from clinical specimens was determined by using the Mycobacteria Growth Indicator Tube (MGIT). These parameters were compared to those assessed by the radiometric BACTEC 460 TB system and by cultivation on solid media. Clinical specimens (n = 1,500) were pretreated with N-acetyl-L-cysteine (NALC)-NaOH. The contamination rates for MGITs were 2.0% (center 1), 13.8% (center 2), and 6.1% (center 3). A total of 180 mycobacterial isolates were detected (M. tuberculosis complex, n = 113; nontuberculous mycobacteria [NTM], n = 67). When using a combination of liquid and solid media (the current "gold standard" for culture), MGIT plus solid media detected 156 (86.7%) of the isolates, whereas BACTEC plus solid media recovered 168 (93.3%) of all AFB. Between these two gold standards there was no statistically significant difference (P > 0.05). The combination of MGIT plus BACTEC detected 171 (95.0%) of all isolates (compared with MGIT plus solid media, P < 0.01; compared with BACTEC plus solid media, P > 0.05). Considering the efficacies of the different media separately, MGIT was superior to solid media (although not significantly; P > 0.05) in detecting AFB but was inferior to the BACTEC system (P < 0.01). The mean time to the detection of M. tuberculosis complex was 9.9 days with MGIT, 9.7 days with BACTEC, and 20.2 days with solid media. NTM needed, on average, 11.9, 13.0, and 22.2 days to appear by the three methods, respectively. In conclusion, MGIT proved to be a valuable alternative to the radiometric cultivation system.

[Acquired cutaneous osteomatosis. A primary monomelic form]. / Ostéomatose cutanée acquise: une forme monomélique primitive.

Eight cases of sporadic acquired primary osteoma cutis have been reported in the literature. Age at onset varies from 16 to 55 years with a mean of about 35 years. The sex ratio is 1 and a wide range of localizations have been reported. There is no known treatment. We report a new case of primary osteoma cutis observed in an adult. The monomelic feature of this case has not been reported previously. The patient was 76 years old and had multiple painless, stone-like formations at several sites on the left thigh and leg since the age of 40. Histological examination of skin biopsies showed a perfectly differentiated bone tissue in the dermal layer. There was no similar family history nor abnormal morphotype. Likewise, the absence of laboratory signs of pseudohypoparathyroidism, together with the late and spontaneous onset allowed us to eliminate hereditary Albright's osteodystropy or secondary osteomatosis due to a local pathological process. Despite the late onset, the monomelic character of the osteomas observed and the association of hemicorporeal hypertrophy and linear basocellular naevi reported in the literature would suggest a hamartomatous origin rather than a metaplasic process in this patient.

A quantitative study of the routes of blood flow to the tibial diaphysis after an osteotomy.

Techniques of tissue exclusion have been used previously in qualitative investigations of the vascularity of long bones, after experimental fracture; we quantified their effects on bone blood flow in rabbits. Thirty-six adult rabbits were divided into three groups in which flow was measured, with the microsphere technique, 1 and 2 weeks after osteotomy. In Group 1, osteotomy of the tibial shaft only was done; in Group 2, osteotomy was done with exclusion of the periosteum and muscle by a silicone rubber sheath; and in Group 3, osteotomy was done with exclusion of the marrow by reaming and insertion of an intramedullary nail. All involved limbs were immobilized in a cast. In Group 1, cortical flow increased but marrow flow did not change, which suggests that the changes in cortical flow were mediated by a supply paralleling that of the marrow. In Group 2, the changes in cortical flow were abolished, which implies that this parallel supply is from the periosteum and extraosseous tissues. In Group 3, cortical flow was not significantly reduced, which demonstrates recruitment of this periosteal and extraosseous supply. These results lend support to the hypothesis that the blood supply to the healing diaphysis is principally from the periosteum and extraosseous tissues during the early peak period of blood flow.

Cast immobilization and tibial diaphyseal blood flow: an initial study.

The effect of cast immobilization on blood flow to the tibial diaphysis was studied by the microsphere method, both before and after casting of one hindlimb of adult New Zealand White rabbits. Preliminary studies were undertaken to investigate the possibility of the reduction of tibial flow by the microspheres used for the control measurements of blood flow. There were no significant differences in the flows to the tibial diaphysis or skeletal muscle between the immobilized and control limbs after either 1 or 2 weeks. This similarity between control and experimental limbs indicates that immobilization had no major effect on tibial blood flow over and above the systemic effects of the procedure.